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Abstract:

The invention relates to a method for transmitting and a method for
reconstructing channel quality information in a communication system.
Further, the invention also provides a transmitter and receiver
performing these methods, respectively. The invention suggests a scheme
for communicating channel quality measures that on the one hand allows
for an accurate reconstruction of the channel quality measures at the
receiver and on the other hand requires an acceptable transmission
overhead. This is achieved by partitioning channel quality measures into
at least two partitions and to compress the values partition-wise, for
example, by means of a discrete cosine transform and the transmission of
only a subset of the resulting coefficients.

Claims:

1. A transmitter for transmitting a periodic report of channel quality
information to a receiving entity within a communication system, the
transmitter comprising: a transmitting unit configured to transmit first
channel quality information reports reporting an average of channel
qualities for resource blocks at a first reporting frequency, and to
transmit a second channel quality information report for a preferred
subset of resource blocks, wherein the transmitter is configured to
transmit the second channel quality information report between the first
channel quality information reports.

2. The transmitter according to claim 1, wherein the transmitting unit is
further configured to transmit a plurality of second channel quality
information reports for the preferred subset of resource blocks at a
second reporting frequency.

3. The transmitter according to claim 2, wherein the first reporting
frequency is different from the second reporting frequency.

4. The transmitter according to claim 3, wherein the first reporting
frequency is more frequent than the second reporting frequency.

5. A method for transmitting a periodic report of channel quality
information to a receiving entity within a communication system, the
method comprising the steps of: transmitting first channel quality
information reports reporting an average of channel qualities for
resource blocks at a first reporting frequency, and transmitting a second
channel quality information report for a preferred subset of resource
blocks, wherein the second channel quality information report is
transmitted between the first channel quality information reports.

6. The method according to claim 5, wherein a plurality of second channel
quality information reports for the preferred subset of resource blocks
are transmitted at a second reporting frequency.

7. The method according to claim 6, wherein the first reporting frequency
is different from the second reporting frequency.

8. The method according to claim 7, wherein the first reporting frequency
is more frequent than the second reporting frequency.

9. A receiver for receiving a periodic report of channel quality
information from a transmitting entity within a communication system, the
receiver comprising: a receiving unit configured to receive first channel
quality information reports reporting an average of channel qualities for
resource blocks at a first reporting frequency, and to receive a second
channel quality information report for a preferred subset of resource
blocks, wherein the receiving unit is configured to receive the second
channel quality information report between the first channel quality
information reports.

10. The receiver according to claim 9, wherein the receiving unit is
further configured to receive a plurality of second channel quality
information reports for the preferred subset of resource blocks at a
second reporting frequency.

11. The receiver according to claim 10, wherein the first reporting
frequency is different from the second reporting frequency.

12. The receiver according to claim 11, wherein the first reporting
frequency is more frequent than the second reporting frequency.

13. A method for receiving a periodic report of channel quality
information from a transmitting entity within a communication system, the
method comprising the steps of: receiving first channel quality
information reports reporting an average of channel qualities for
resource blocks at a first reporting frequency, and receiving a second
channel quality information report for a preferred subset of resource
blocks, wherein the second channel quality information report is received
between the first channel quality information reports.

14. The method according to claim 13, wherein a plurality of second
channel quality information reports for the preferred subset of resource
blocks are received at a second reporting frequency.

15. The method according to claim 14, wherein the first reporting
frequency is different from the second reporting frequency.

16. The method according to claim 15, wherein the first reporting
frequency is more frequent than the second reporting frequency.

Description:

FIELD OF THE INVENTION

[0001] The invention relates to a method for transmitting and a method for
reconstructing channel quality information in a communication system.
Further, the invention also provides a transmitter and receiver
performing these methods, respectively.

TECHNICAL BACKGROUND

Packet-Scheduling and Shared Channel Transmission

[0002] In wireless communication systems employing packet-scheduling, at
least part of the air-interface resources are assigned dynamically to
different users (mobile stations--MS). Those dynamically allocated
resources are typically mapped to at least one shared data channel
(SDCH). A shared data channel may for example have one of the following
configurations: [0003] One or multiple codes in a CDMA (Code Division
Multiple Access) system are dynamically shared between multiple MS.
[0004] One or multiple subcarriers (subbands) in an OFDMA (Orthogonal
Frequency Division Multiple Access) system are dynamically shared between
multiple MS. [0005] Combinations of the above in an OFCDMA (Orthogonal
Frequency Code Division Multiplex Access) or a MC-CDMA (Multi
Carrier-Code Division Multiple Access) system are dynamically shared
between multiple MS.

[0006] FIG. 1 shows a resource-scheduling system on a communication
channel for systems with e.g., a single shared data channel. A
transmission time interval (TTI) reflects the smallest interval at which
the scheduler (e.g., the Physical Layer or MAC Layer Scheduler) performs
the dynamic resource allocation (DRA). In FIG. 1, a TTI equal to one
subframe (also referred to as a time slot) is assumed. It should be noted
that generally a TTI may also span over multiple subframes.

[0007] Further, the smallest unit of radio resources (also referred to as
a resource block), that can be allocated in OFDMA systems, is typically
defined by one TTI in the time domain and by one subcarrier/subband in
the frequency domain. Similarly, in a CDMA system this smallest unit of
radio resources is defined by a TTI in the time domain and a code in the
code domain.

[0008] In OFCDMA or MC-CDMA systems, this smallest unit is defined by one
TTI in time domain, by one subcarrier/subband in the frequency domain and
one code in the code domain. Note that dynamic resource allocation may be
performed in the time domain and in the code/frequency domain.

[0009] The main benefits of packet-scheduling are the multi-user diversity
gain by time domain scheduling (TDS) and dynamic user rate adaptation
(DRA).

[0010] Assuming that the channel conditions of the users change over time
due to fast (and slow) fading, at a given time instant the scheduler can
assign available resources (codes in case of CDMA, subcarriers/subbands
in case of OFDMA) to users having good channel conditions in time domain
scheduling.

Specifics of DRA and Shared Channel Transmission in OFDMA

[0011] Additionally to exploiting multi-user diversity in time domain by
Time Domain Scheduling (TDS), in OFDMA multi-user diversity can also be
exploited in frequency domain by Frequency Domain Scheduling (FDS). This
is because the OFDM signal is constructed out of multiple narrowband
subcarriers (typically grouped into subbands) in frequency domain, which
can be assigned dynamically to different users. By this, the frequency
selective channel properties due to multi-path propagation can be
exploited to schedule users on frequencies (subcarriers/subbands) on
which they have a good channel quality (multi-user diversity in frequency
domain).

[0012] In an OFDMA system the bandwidth is divided into multiple subbands
for practical reasons that consist out of multiple subcarriers. I.e., the
smallest unit on which a user may be allocated would have a bandwidth of
one subband and a duration of one subframe (which may correspond to one
or multiple OFDM symbols), which is denoted as a resource block (RB).
Typically a subband consists of consecutive subcarriers. However in some
cases it is desired to form a subband out of distributed non-consecutive
subcarriers. A scheduler may also allocate a user over multiple
consecutive or non-consecutive subbands and/or subframes.

[0013] For the 3GPP Long Term Evolution (see 3GPP TR 25.814: "Physical
Layer Aspects for Evolved UTRA", Release 7, v. 7.0.0, June
2006--available at http://www.3gpp.org and incorporated herein by
reference), a 10 MHz system may consist of 600 subcarriers with a
subcarrier spacing of 15 kHz. The 600 subcarriers may then be grouped
into 24 subbands (each containing 25 subcarriers), each subband occupying
a bandwidth of 375 kHz. Assuming that a subframe has a duration of 0.5
ms, a resource block (RB) would span over 375 kHz and 0.5 ms according to
this example.

[0014] In order to exploit multi-user diversity and to achieve scheduling
gain in frequency domain, the data for a given user should be allocated
on resource blocks on which the user has a good channel condition.
Typically, those resource blocks are located close to each other and,
therefore, this transmission mode is also denoted as localized mode (LM).
FIG. 2 shows an exemplary data transmission to users in an OFDMA system
in localized mode (LM) having a distributed mapping of Layer 1/Layer 2
control signalling.

[0015] Alternatively, the users may be allocated in a distributed mode
(DM). In this configuration a user (mobile station) is allocated on
multiple resource blocks, which are distributed over a range of resource
blocks. In distributed mode a number of different implementation options
are possible. For exemplary purposes a data transmission to users in an
OFDMA system in distributed mode (DM) having a distributed mapping of
Layer 1/Layer 2 control signalling is shown in FIG. 3.

Link Adaptation

[0016] In mobile communication systems link adaptation is a typical
measure to exploit the benefits resulting from dynamic resource
allocation. One link adaptation technique is AMC (Adaptive Modulation and
Coding). Here, the data-rate per data block or per scheduled user is
adapted dynamically to the instantaneous channel quality of the
respective allocated resource by dynamically changing the modulation and
coding scheme (MCS) in response to the channel conditions. This may
require a transmitter to have or obtain a channel quality estimate for
the link to the respective receiver. Typically hybrid ARQ (HARM)
techniques are employed in addition. In some configurations it may also
make sense to use fast/slow power control.

Channel Quality Information (CQI) Transmission

[0017] In a multi-user centrally managed system, a scheduler assigns
transmission resources to several users as has been outlined above. Since
generally the channel conditions for different users will vary over at
least time and frequency, some sort of channel state or channel quality
information is required at the scheduler, preferably transmitted from
each user equipment device to the scheduler entity.

[0018] For most multi-user scheduler algorithms (except Round Robin), the
most accurate channel state information should be for the strongest
resource blocks, to optimally assign a resource to a user where the
channel exhibits a good quality. This will further be used in case that
for transmission of data, the modulation or coding scheme is adapted to
the channel quality, to increase the spectral efficiency, i.e., in cases
where link adaptation is performed.

[0019] Generally the CQI is transmitted from a transmitting entity to a
receiver entity. In the context of 3 G radio network as in UMTS, where a
NodeB may act as the multi-user management entity, as well as a
multi-cell management entity, the CQI for the downlink transmission chain
is obtained (estimated) by a user equipment (UE), which subsequently
transmits CQI to a NodeB. Therefore with respect to CQI transmission the
user equipment acts as the transmitter entity, and the NodeB as the
receiver entity.

Full Feedback

[0020] In case a full feedback is transmitted, i.e., the CQI information
is not compressed prior to transmission, a CQI value for each of the
Nrb resource blocks is transmitted, giving the highest accuracy of
information at a very high cost of required transmission bits. To get a
rough estimate of the overhead on the CQI feedback information, a system
based on the following configurations may be considered: the
communication system is equipped with 2×2 MIMO (Multiple Input
Multiple Output) using PARC (Per Antenna Rate Control), 20 MHz
transmission bandwidth (48 Resource Blocks), 0.5 ms CQI feedback
interval, 1/3 rate turbo encoding, no-repetitions or puncturing, and with
24 bit CRC attached. The total CQI feedback overhead of this
configuration would be 2.904 Mbps per user.

CQI Compression

[0021] One approach to reduce the overhead induced by CQI signalling has
been suggested in 3GPP RAN WG#1 Tdoc. R1-061777, "DCT based CQI reporting
scheme", available at http://www.3gpp.org and incorporated herein by
reference. The document proposes a scheme using a Discrete Cosine
Transform (DCT) to concentrate information into a small number of
coefficients and discusses different mechanisms which coefficients, to
transmit.

Strongest-M DCT and First-M DCT

[0022] The "Strongest-M" DCT scheme transmits the DC component of the
transformation and in addition M-1 most significant DCT coefficients.
Assuming that M is known to transmitter and receiver, only indices of the
transmitted coefficients as well as the values of the transmitted
coefficients need to be signalled. If M is not known by either the
transmitter or the receiver, the value of M may have to be signalled as
well.

[0023] The "First-M" DCT scheme transmits the M coefficients with the M
lowest index values. Assuming that M is known to transmitter and
receiver, only the values of the transmitted coefficients need to be
signalled. If M is not known by either the transmitter or the receiver,
the value of M may have to be signalled as well.

[0024] An example of a channel snapshot and an exemplary reconstruction of
the channel power using "Strongest 5" DCT scheme is shown in FIG. 8. The
corresponding DCT of the complete ("Full DCT") and compressed ("Strongest
5" DCT) channel information is shown in FIG. 9. While the channel state
may be reconstructed perfectly if all DCT coefficients ("Full DCT") are
transmitted, the channel state reconstruction will generally be
suboptimum if only a subset of the DCT coefficients is transmitted. The
choice of which DCT coefficients are transmitted will affect the accuracy
of the reconstructed channel state.

[0025] In the "Strongest 5" DCT scheme, only the 5 components with the
largest magnitude are chosen in the compression scheme. Since the DC
component may be of increased importance, and as it can usually be
expected to be among the strongest components anyway, it may be
preferable to always transmit the DC coefficient. A bitmap that shows
which 5 of the 24 DCT components have the largest magnitude is given in
FIG. 10, where a "1" value that the DCT component of that particular
index belongs to one of the M largest magnitude coefficients.

[0026] It is a matter of convention whether the DCT components are labeled
(numbered) from 0 to Nrb-1 or from 1 to Nrb, or similar. Either
way usually the DCT component with the lowest index is commonly referred
to as the "DC coefficient" or "DC component" (DC=Direct Current). Without
loss of generality a numbering ranging from 1 to Nrb is assumed in
the examples described herein.

[0027] While the above mentioned approaches for transmitting the CQI
information are based on performing a DCT on the channel state
information and encoding the resulting coefficients, there also exist
other schemes where the channel state information, i.e., the individual
power levels per resource block are encoded without performing a
transformation.

[0028] 3GPP RAN WG#1 Tdoc. R1-061819, "Overhead reduction of UL CQI
signalling for E-UTRA DL", available at http://www.3gpp.org and
incorporated herein by reference, discusses a "Best-M" scheme for
feedback reduction of channel quality signalling where a UE reports a
label which indicates the M resource blocks with highest signal quality
and additionally a single channel quality indicator for these resource
blocks. Assuming that M is known to the transmitter and the receiver,
signalling of the M selected indices and the selected M values is needed
in a CQI report.

[0029] A further scheme referred to as "Best M Individual" scheme reports
the power for each of the M best resource blocks, and average power for
other resource blocks. Assuming that M is known to the transmitter and
the receiver, signalling of the M selected indices, the selected M
values, and the average value is needed in a CQI report. An exemplary
bitmap that signals the best 5 out of 24 resource blocks is shown in FIG.
13.

[0030] A further scheme referred to as "Best M Average" reports the
average power for M best resource blocks, and average power for other
resource blocks. Assuming that M is known to the transmitter and the
receiver, signalling of the M selected indices and the two average values
is needed in a CQI report. An exemplary bitmap that signals the best 5
out of 24 resource blocks is shown in FIG. 13.

[0031] An example of a channel snapshot and an exemplary reconstruction of
the channel power using a "Best 5 Individual" scheme and a "Best 5
Average" scheme are shown in FIG. 11 and in FIG. 12, respectively. As can
be seen, the "Best 5 Individual" scheme manages to give exact information
for the 5 strongest resource blocks (number 8, 9, 10, 18, 19), but quite
substantial deviations from the correct value for all other resource
blocks. The "Best 5 Average" scheme gives by chance quite accurate
information for resource blocks 18 and 19, while we can identify larger
deviations--both better and worse--from the correct value for resource
blocks 8, 9, and 10. Likewise, for all other resource blocks the
reconstructed value may exhibit large differences from the correct
values.

Average CQI

[0032] Another scheme to reduce the CQI values is to determine the average
CQI value and transmit this average value. This may be interpreted as a
special case of a Best M=Nrb Average or Best M=0 Average scheme. It
requires the least amount of transmitted information, however it also
offers a generally very low accuracy with respect to the reconstructed
resource block-wise channel quality information.

Signalling

[0033] Obviously, there is a need for using information symbols to convey
the CQI from the transmitter to the receiver. Without loss of generality,
it may be assumed that bits can be used as information symbols. Using the
notations defined in subsequent sections, the number of bits required for
such signalling is illustrated in Table 1.

[0034] As can be calculated from Table 1 and has been indicated above, the
full feedback scheme requires a very high amount of bits to signal the
CQI. This requirement may be too high to fulfill in a transmission
system, particularly in cellular mobile radio systems where a large
number of entities have to report CQI values.

[0035] Also DCT-based schemes do not offer an optimal solution for
transmitting the CQI information. Since only a limited number of
coefficients is transmitted in a DCT compression scheme, the
reconstruction at the receiver (which typically offers scheduling
functions) is generally not optimum for any resource block. Consequently
there will be deviations for the strongest resource blocks, which will
result in erroneous scheduler decisions or suboptimum adaptive modulation
and coding decisions by the link adaptation entity. Consequently the
spectral efficiency is reduced.

[0036] In the "Best M Individual" scheme, very detailed information on the
channel state is transmitted for the strongest M resource blocks. For all
other resource blocks, the information available at the scheduler is
extremely rudimentary.

[0037] Particularly in case that M is rather small, a problem occurs if a
user is assigned more resource blocks than M resource blocks. In this
case, some allocated resources are only allocated according to an average
resource block quality, which certainly is suboptimum. Furthermore, a
subsequent link adaptation would also be based on such an average value,
resulting in suboptimum link adaptation and consequently in reduced
spectral efficiency. This problem may be circumvented by a high number M,
however at the drawback that a lot of feedback signalling is required in
this case. Therefore another potential problem is to suggest a coding
scheme that requires a small amount of feedback signalling.

[0038] In the "Best M Average" scheme, the problems are two-fold. On the
one hand, a small number of M will result in similar problems as a small
M in the "Best M Individual" scheme. Additionally, the accuracy of the
best M resource blocks reported is not as high as in the "Best M
Individual" scheme, further deteriorating the accuracy of scheduling or
link adaptation performance.

[0039] On the other hand, a simple increase of M is not guaranteed to
improve the behavior of the "Best M Average" scheme. Even though the
number of resource blocks which are contained within the signalled set
increases, the averaging over those M resources will decrease the
accuracy for those resource blocks. Therefore there is an optimum M for
which the number and level of detail provide the most accurate allocation
or link adaptation.

[0040] In any case, finding this value of M may not be trivial in a mobile
or cellular environment, and--in addition--even when having found an
appropriate M value, the achievable data transmission throughput in data
transmission is generally bad because of the averaging feature of this
scheme.

[0041] It should be obvious to those skilled in the art that the
information conveyed by the average CQI scheme is of very low accuracy.
In order to perform meaningful resource scheduling or link adaptation
using CQI-dependant modulation or coding schemes, a higher accuracy than
that provided by the average scheme has to be available.

SUMMARY OF THE INVENTION

[0042] One object of the invention is to suggest a scheme for transmitting
channel quality measures from a transmitter to a receiver that may
mitigate at least one of the problems outlined above.

[0043] Another object of the invention is to suggest a scheme for
communicating channel quality measures that on the one hand allows for an
accurate reconstruction of the channel quality measures at the receiver
and on the other hand requires an acceptable transmission overhead.

[0044] At least one of these objects is solved by the subject matter of
the independent claims. Advantageous embodiments of the invention are
subject matters of the dependent claims.

[0045] According to one aspect of the invention, channel quality feedback
measures for a channel (e.g., per resource unit of the channel) are
divided into distinct partitions. Each partition consists only of a
subset of the channel quality feedback measures. The partitioning of the
channel quality feedback measures may allow for reducing the amount of
overhead that needs to be attributed to the signalling of channel quality
information, as (in some embodiments) the partitioning may be
advantageously used to further reduce the amount of signalling
information. Further, the partitioning may allow for a more accurate
reconstruction of the channel state at the receiver, from which
scheduling and link adaptation may benefit.

[0046] Another aspect of the invention relates to the receiver that
"inverts" the encoding (compression) scheme to reconstruct the channel
quality measures. In some exemplary embodiments of the invention, a
scheduler may utilize the information on the channel condition to
schedule air interface resources of transmitters that are served by the
scheduler. Moreover, alternatively or in addition thereto, the
reconstructed channel estimate may also be employed to determine the link
adaptation to be applied to data transmissions on a wireless channel.

[0047] A further aspect of the invention is the use of some (re)ordering
scheme that is reordering the channel quality measures prior to their
transmission as channel quality information. According to this aspect the
channel quality measures of a channel may be (re)ordered so that encoding
of the measures yields the most accurate reconstruction of the measures
at the receiver. The (re)ordering mechanism may also be combined with the
other aspects of the invention outlined above.

[0048] According to one exemplary embodiment of the invention a method for
transmitting channel quality information in a communication system is
provided. In this method the channel quality values (e.g., of the
plurality of resource units) may be first partitioned into at least two
partitions. Then the channel quality values of at least one of the at
least two partitions may be transformed to obtain channel quality
coefficients. These coefficients may be encoded to obtain signalling
information on the channel quality which is signalled to a receiving
entity.

[0049] In one embodiment, the number of the channel quality coefficients
obtained for a respective partition by transformation is equal to the
number of the channel quality values of the respective partition.

[0050] Further, the transformation used for transforming of the channel
quality values may for example be a discrete cosine transformation (DCT),
a Fourier transformation or a transformation based on a continuous
function.

[0051] Another embodiment of the invention relates to situations where the
channel quality values are encoded. Channel quality information may be
transmitted in a communication system by first partitioning channel
quality values of the plurality of resource units into at least two
partitions, encoding the channel quality values to obtain signalling
information on the channel quality and signalling the signalling
information on the channel quality to a receiving entity.

[0052] In one embodiment, the channel quality values may be partitioned by
comparing the individual channel quality values to at least one channel
quality threshold value. Typically, one threshold value per boundary of
neighboring partitions may be defined.

[0053] Further, in another embodiment the channel quality values are
partitioned by allocating a given number of channel quality values to a
respective partition. This number of channel quality values in a
partition may for example be preconfigured. The predefinition of the
number of values per partition may for example be advantageous in that no
signalling of the number of elements in the partition is necessary.

[0054] Typically, it may also be advantageous if the sum of the
cardinality of the at least two partitions is equal to the number of
channel quality values, i.e., all channel quality values are allocated to
either one of the at least two partitions.

[0055] In a further embodiment of the invention, the channel quality
coefficients or values may be encoded by compressing the channel quality
coefficients or values, respectively, of at least one partition.

[0056] In one embodiment, the signalling information on the channel
quality may indicate a number of encoded channel quality coefficients or
values to the receiving entity that is smaller than the number of the
channel quality coefficients or values, respectively, in the at least two
partitions. Thereby, according to an exemplary variation of this
embodiment, the channel quality coefficients or values are encoded by
selecting the minimum number of channel quality coefficients or values,
respectively, from a partition yielding a power level equal to or higher
than a threshold power level.

[0057] According to another embodiment of the invention, the channel
quality coefficients or values may be encoded by selecting a subset of
the channel quality coefficients or values, respectively, from at least
two partitions. Thereby, according to an exemplary variation of the
embodiment, the cardinality of a first subset of the subsets may depend
on the cardinality of a second subset of the subsets.

[0058] In another embodiment of the invention, it is suggested that prior
to encoding at least one combined channel quality coefficient or value
derived from at least two channel quality coefficients or values,
respectively, is determined and that the at least one combined channel
quality coefficient or value is encoded. This may for example be useful
in order to reduce the signalling overhead by combining all or a subset
of channel quality values/coefficients to one or more averaged
values/coefficients prior to transmission.

[0059] Another option to encode the channel quality values or coefficients
according to another embodiment of the invention is to encode same by
selecting a predefined number of channel quality coefficients or values,
respectively, from the at least two partitions. Thereby, the number of
selected channel quality coefficients or values from a first partition of
the at least two partitions may for example depend on at least one
predetermined constraint, while the remaining number of selected channel
quality coefficients or values may be selected from at least the second
partition of the at least two partitions.

[0060] Generally, the partitions may be encoded according to the same or
according to different encoding schemes.

[0061] Moreover, in another embodiment of the invention, the channel
quality coefficients or values of at least two partitions may be jointly
encoded. This may for example be implemented as follows. A respective
channel quality coefficient or value in a respective partition may be
identified by an index. The channel quality coefficients or values may be
jointly encoded by selecting channel quality coefficients or values,
respectively, from at least two partitions having the same indices.

[0062] If the at least two partitions do not have equal cardinality, it
may be beneficial to add padding coefficients or values to a partition so
as to obtain at least two partitions having same cardinality.

[0063] In another embodiment, a respective channel quality coefficient or
value in a respective partition may be indexed. In this embodiment
averaged channel quality coefficients or values are determined prior to
encoding and the averaged channel quality coefficients or values are
encoded.

[0064] For example, the averaged channel quality coefficients or values
may be determined by a coefficient-wise or value-wise averaging of
channel quality coefficients or values, respectively from at least two
partitions. Further, it may be foreseen that channel quality coefficients
or values, respectively from at least two partitions having the same
index are averaged coefficient-wise or value-wise, respectively. This may
for example allow for reducing the index signalling overhead.

[0065] In another embodiment of the invention, the channel quality
coefficients or values of at least one partition may be reordered prior
to their encoding. For example, reordering is performed according to one
of predefined reordering maps or according to one of predefined
interleaving schemes.

[0066] As indicated previously, a respective channel quality coefficient
or value in a respective partition may be identified by an index. In a
further embodiment of the invention the signalling information on the
channel quality may indicate the indices of the encoded channel quality
coefficients or values of a respective partition included in the
signalling information on the channel quality. In a variation of this
embodiment, the signalling information on the channel quality may further
comprise information on the values of the encoded channel quality
coefficients or values.

[0067] According to another embodiment of the invention, at least one of
the at least two partitions may be partitioned prior to transformation or
encoding to obtain at least two sub-partitions. This may be useful in
situations where for example a first partitioning is performed according
to the number of antennas (e.g., one partition of channel quality values
per antenna) and then each of the partitions is again divided into
sub-partitions (e.g., based on a threshold value). Further, the channel
quality values in at least one sub-partition may by transformed prior to
encoding to obtain channel quality coefficients for a respective
sub-partition.

[0068] Another embodiment of the invention relates to a method for
reconstructing channel quality values. According to this method a
receiving entity may receive signalling information on the channel
quality from a transmitting entity. This signalling information on the
channel quality may be decoded by the receiving entity to obtain channel
quality coefficients of at least two partitions. Further, the channel
quality coefficients of each partition may be transformed to obtain
channel quality values for a respective partition, and the channel
quality values may be reconstructed using the channel quality values of
at least one partition.

[0069] According to another embodiment, no (inverse) transformation of
channel quality coefficients may be necessary, e.g., due to performing no
transformation on the transmitting entity side. In these cases the
channel quality values may be directly derived from the signalling
information on the channel.

[0070] In a further embodiment, the channel quality values of the
plurality of resource units may be received from a plurality of
transmitting entities. According to this embodiment, the receiver
schedules a respective one (at least one) of the plurality of
transmitting entities taking into account at least the reconstructed
channel quality values signalled by the respective transmitting entity.

[0071] In another embodiment, the receiver may select at least one link
adaptation parameter for link adaptation for a respective one of the
plurality of transmitting entities taking into account at least the
reconstructed channel quality values signalled by the respective
transmitting entity. For example, this at least one link adaptation
parameter may be related to at least one of a modulation and coding
scheme, a configuration of at least one hybrid automatic repeat request
process, and transmission power control.

[0072] Further, according to another embodiment, a management entity may
determine at least one parameter for at least one of partitioning,
encoding, or transformation. Moreover, the management entity may convey
the at least one parameter to the channel quality information transmitter
using a control signal. For example, the management entity may be a base
station (Node B in the UMTS terminology) or may be another network entity
located in the core network or access network of a communication system.

[0073] Another embodiment of the invention provides a transmitter for
transmitting channel quality information in a communication system. This
transmitter may comprise a processing unit for partitioning channel
quality values into at least two partitions. The processing may further
transform the channel quality values of at least one of the at least two
partitions to obtain channel quality coefficients. The transmitter may
also include a coding unit for encoding the channel quality coefficients
to obtain signalling information on the channel quality and a
transmitting unit for signalling the signalling information on the
channel quality to a receiving entity.

[0074] A further embodiment of the invention relates to a transmitter
comprising a processing unit for partitioning channel quality values of
the plurality of resource units into at least two partitions, and a
coding unit for encoding the channel quality values to obtain signalling
information on the channel quality. Further, the transmitter may comprise
a transmitting unit for signalling the signalling information on the
channel quality to a receiving entity.

[0075] Furthermore, in another embodiment the transmitter may have means
to perform the steps of the method for transmitting channel quality
information in a communication system according to one of the various
embodiments described herein.

[0076] According to another embodiment, a receiver for reconstructing
channel quality values is provided. The receiver may comprise a receiving
unit for receiving signalling information on the channel quality from a
transmitting entity. Further, the receiver may have a decoding unit for
decoding the signalling information on the channel quality to obtain
channel quality coefficients of at least two partitions, and a processing
unit for transforming the channel quality coefficients of each partition
to obtain channel quality values for a respective partition. The
processing unit may reconstruct the channel quality values using the
channel quality values of at least one partition.

[0077] In another embodiment, a receiver for reconstructing channel
quality values may comprise a receiving unit for receiving signalling
information on the channel quality from a transmitting entity, and a
decoding unit for decoding the signalling information on the channel
quality to obtain channel quality values of at least two partitions.
Moreover, the receiver according to this embodiment may comprise a
processing unit for reconstructing the channel quality values of a
plurality of resource units using the channel quality values of at least
one partition.

[0078] Furthermore, in another embodiment the receiver may contain means
to perform the steps of the method for reconstructing channel quality
values according to one of the various embodiments described herein.

[0079] Another embodiment of the invention relates to a computer-readable
medium storing instructions that, when executed by processor of a
transmitter, cause the transmitter to transmit channel quality
information in a communication system.

[0080] The transmitter may be caused to transmit channel quality
information in a communication system by partitioning channel quality
values into at least two partitions, transforming the channel quality
values of at least one of the at least two partitions to obtain channel
quality coefficients, encoding the channel quality coefficients to obtain
signalling information on the channel quality and signalling the
signalling information on the channel quality to a receiving entity.

[0081] In another embodiment, a transmitter may be caused to transmit
channel quality information in a communication system by partitioning
channel quality values into at least two partitions, encoding the channel
quality values to obtain signalling information on the channel quality
and signalling the signalling information on the channel quality to a
receiving entity.

[0082] A further embodiment relates to a computer-readable medium storing
instruction that, when executed by the processor of the transmitter cause
the transmitter to perform the steps of the method for transmitting
channel quality values according to one of the various embodiments
described herein.

[0083] Another computer-readable medium according to an embodiment of the
invention stores instruction that, when executed by a processor of a
receiver, cause the receiver to reconstruct channel quality values.

[0084] The receiver may be caused to reconstruct channel quality values by
receiving signalling information on the channel quality from a
transmitting entity, decoding the signalling information on the channel
quality to obtain channel quality coefficients of at least two
partitions, and transforming the channel quality coefficients of each
partition to obtain channel quality values for a respective partition,
and reconstructing the channel quality values of the plurality of
resource units using the channel quality values of at least one
partition.

[0085] In another embodiment, the receiver may be caused to reconstruct
channel quality values by receiving signalling information on the channel
quality from a transmitting entity, decoding the signalling information
on the channel quality to obtain channel quality values of at least two
partitions, and reconstructing the channel quality values of the
plurality of resource units by using the channel quality values of at
least one partition.

[0086] A further embodiment relates to a computer-readable medium storing
instruction that, when executed by the processor of the receiver cause
the receiver to perform the steps of the method for receiving channel
quality information in a communication system according to one of the
various embodiments described herein.

[0087] Another embodiment of the invention relates to a method for
transmitting channel quality information in a communication system. The
transmitting entity may reorder channel quality values, and may then
transform the reordered channel quality values to obtain channel quality
coefficients. Further, the channel quality coefficients may be encoded to
obtain signalling information on the channel quality which may be
signalled to a receiving entity.

[0088] In a further embodiment, the reordering comprises determining a
number of sequences of reordered channel quality values by employing
different reordering mappings. Moreover, the transmitting entity may
choose a reordering mapping for which the reordered channel quality
values fulfill an optimality criterion prior or after transformation.

[0089] Furthermore, in another embodiment of the invention, the reordering
scheme is signalled to the receiving entity, for example, within the
channel quality information.

[0090] In another embodiment, the reordering mappings are defined by at
least one reordering parameter.

[0091] A further embodiment of the invention relates to a method for
reconstructing channel quality values. A receiving entity may first
receive signalling information on the channel quality from a transmitting
entity and may decode the signalling information on the channel quality
to obtain channel quality coefficients. The receiving entity may
transform the channel quality coefficients, and reconstruct channel
quality values by reordering the transformed channel quality
coefficients.

[0092] Thereby, another embodiment foresees that the transformed channel
quality coefficients are reordered according to a mapping scheme. The
mapping scheme may, for example, be indicated within the channel quality
information or in control signalling received by the receiving entity.

[0093] Another embodiment of the invention relates to a transmitter for
transmitting channel quality information in a communication system. The
transmitter comprises a reordering unit for reordering channel quality
values, and a processing unit for transforming the reordered channel
quality values to obtain channel quality coefficients. Further, a coding
unit of the transmitter may encode the channel quality coefficients to
obtain signalling information on the channel quality and a transmission
unit may signal the signalling information on the channel quality to a
receiving entity.

[0094] Another embodiment relates to a receiver for reconstructing channel
quality values. The receiver may include a receiving unit for receiving
signalling information on the channel quality from a transmitter, and
further a decoding unit for decoding the signalling information on the
channel quality to obtain channel quality coefficients. The receiver may
also comprise a processing unit for transforming the channel quality
coefficients, and a reordering unit for reconstructing channel quality
values by reordering the transformed channel quality coefficients.

[0095] Another embodiment of the invention relates to a computer readable
medium storing instruction that, when executed by a processor of a
transmitter, cause the transmitter to transmit channel quality
information in a communication system, by reordering channel quality
values, transforming the reordered channel quality values to obtain
channel quality coefficients, encoding the channel quality coefficients
to obtain signalling information on the channel quality and signalling
the signalling information on the channel quality to a receiving entity.

[0096] A further embodiment of the invention relates to a computer
readable medium storing instruction that, when executed by a processor of
a receiver, cause the receiver to transmit channel quality information in
a communication system, by receiving signalling information on the
channel quality from a transmitter, decoding the signalling information
on the channel quality to obtain channel quality coefficients,
transforming the channel quality coefficients, and reconstructing channel
quality values by reordering the transformed channel quality coefficients

BRIEF DESCRIPTION OF THE FIGURES

[0097] In the following the invention is described in more detail in
reference to the attached figures and drawings. Similar or corresponding
details in the figures are marked with the same reference numerals.

[0098] FIG. 1 shows an exemplary channel structure of an OFDMA system and
a dynamic allocation of radio resources on a transmission time interval
basis to different users, and

[0099] FIG. 2 shows an exemplary data transmission to users in an OFDMA
system in localized mode (LM) having a distributed mapping of Layer
1/Layer 2 control signalling,

[0100]FIG. 3 shows an exemplary data transmission to users in an OFDMA
system in distributed mode (DM) having a distributed mapping of Layer
1/Layer 2 control signalling,

[0101] FIG. 4 shows a flow chart of a method for transmitting channel
quality information according to an embodiment of the invention,

[0102]FIG. 5 shows a flow chart of a method for transmitting channel
quality information according to an embodiment of the invention, wherein
no transformation of channel quality values is performed,

[0103]FIG. 6 shows a flow chart of a method for reconstructing channel
quality values of a channel from received channel quality information
according to an embodiment of the invention,

[0104] FIG. 7 shows a flow chart of a method for reconstructing channel
quality values of a channel from received channel quality information
according to an embodiment of the invention, wherein no transformation of
channel quality coefficients to channel quality values is performed,

[0105]FIG. 8 shows an exemplary snapshot of channel quality values (here
"power") for a sequence of 24 resource blocks for a radio channel, and
the corresponding reconstruction using compressed Strongest 5 DCT
transmission,

[0106]FIG. 9 shows the full DCT and the strongest 5 DCT components for
the channel in FIG. 8,

[0107]FIG. 10 shows a bitmap to indicate which DCT coefficients are the
strongest according to FIG. 9,

[0108]FIG. 11 shows an exemplary snapshot of channel power values for a
sequence of 24 resource blocks for a radio channel, and the corresponding
reconstruction using a "Best 5 Individual" compression of the channel
quality values,

[0109] FIG. 12 shows an exemplary snapshot of channel power values for a
sequence of 24 resource blocks for a radio channel, and the corresponding
reconstruction using a "Best 5 Average" compression of the channel
quality values,

[0110]FIG. 13 shows a bitmap to indicate which resource blocks have the
best (strongest) channel quality values in FIG. 11 and FIG. 12,

[0111] FIG. 14 shows an exemplary categorization of channel quality
measures (here "power") of a plurality of resource units of a channel
into two partitions according to an exemplary embodiment of the
invention,

[0112]FIG. 15 shows an exemplary bitmap for signalling the affiliation of
resource units to partition for FIG. 14 according to an exemplary
embodiment of the invention, where a "1" denotes affiliation to a first
partition and a "0" denotes affiliation to a second partition,

[0113] FIG. 16 shows the result of partition-wise DCT for the first
partition of channel quality values from FIG. 14, and indicates the three
strongest DCT components that may be chosen for transmission, according
to an exemplary embodiment of the invention,

[0114] FIG. 17 shows the result of partition-wise DCT for the second
partition of channel quality values from FIG. 14, and indicates the three
strongest DCT components that may be chosen for transmission, according
to an exemplary embodiment of the invention,

[0115] FIG. 18 shows an exemplary bitmap for signalling which DCT
components are transmitted for the first partition with respect to the
strongest-three criterion according to FIG. 16 according to an exemplary
embodiment of the invention,

[0116] FIG. 19 shows an exemplary bitmap for signalling which DCT
components are transmitted for the second partition with respect to the
strongest-three criterion according to FIG. 17 according to an exemplary
embodiment of the invention,

[0117] FIG. 20 shows the channel state as in FIG. 14 and a reconstruction
of channel quality values from compressed partition-wise DCT according to
an exemplary embodiment of the invention,

[0118] FIG. 21 shows the channel state as in FIG. 14 and a reconstruction
of channel quality values from compressed partition-wise DCT with reduced
coefficient signalling overhead according to an exemplary embodiment of
the invention,

[0119] FIG. 22 shows an example of an original sequence consisting of only
two distinct SINR values, and the corresponding DCT transform,

[0120] FIG. 23 shows an example how the resource blocks of FIG. 22 may be
grouped into two partitions according to an exemplary embodiment of the
invention,

[0121] FIG. 24 shows the result of partitioning the resource blocks of
FIG. 22 into partition 1, and the corresponding DCT transform of
partition 1, according to an exemplary embodiment of the invention,

[0122] FIG. 25 shows an exemplary bitmap for signalling the strongest DCT
component of the partition 1 DCT of FIG. 22, according to an exemplary
embodiment of the invention,

[0123] FIG. 26 shows the result of partitioning the resource blocks of
FIG. 22 into partition 2, and the corresponding DCT transform of
partition 2 according to an exemplary embodiment of the invention,

[0124] FIG. 27 shows the bitmap to signal the strongest DCT component of
the partition 2 DCT of FIG. 22 according to an exemplary embodiment of
the invention,

[0125] FIG. 28 shows a mobile communication system according to one
embodiment of the invention, in which the ideas of the invention may be
implemented,

[0126]FIG. 29 shows an exemplary flow chart of a method for transmitting
channel quality information using a reordering (re)mechanisms according
to an embodiment of the invention and

[0127]FIG. 30 shows another exemplary flow chart of a method for
transmitting channel quality information using a reordering
(re)mechanisms and transformation of the channel quality values according
to another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0128] Before outlining the concepts and the ideas of the invention
according to different embodiments in further detail, the following
notation used herein should be recognized: [0129] Nrb denotes the
total number of resource unit of a channel, [0130] νi or
νij denotes a channel quality value i, for resource unit i,
where i=1, K, NRB, j may indicate the partition Pj to which the
channel quality value has been assigned [0131] NPi denotes the
number of channel quality values in partition Pi

[0131] P i = { v 1 i , K , v N P i i } ##EQU00004##

denotes a set or partition having NPi channel quality values
[0132] ci or cij denotes a channel quality coefficient i,
j may indicate the transformed partition Tj of the channel quality
coefficient [0133] NTi denotes the number of channel quality
coefficients in a set or transformed partition Ti

[0133] T i = { c 1 i , K , c N T i i } ##EQU00005##

denotes a set or transformed partition having NTi channel
quality coefficients obtained by transforming partition Pi[0134]
Nr denoted the total number of defined (re)ordering algorithms
[0135] NMIMO denotes the total number of MIMO data streams [0136]
Mo denotes the number of channel quality values or coefficients
transmitted for all partitions [0137] Mi denotes the number of
transmitted channel quality values for partition Pi or the number of
transmitted channel quality coefficients for transformed partition
Ti[0138] Ms denotes the sum of transmitted (e.g., after
compression) coefficients for all partitions [0139] Ai denotes
parent partition A [0140] Bi,j denotes sub-partition j belonging to
parent partition Ai[0141] D denotes the number of bits used for
transmission of a single channel quality value νi or channel
quality coefficient ci

[0144] Generally it should be further noted that the term "compression" as
used herein refers to a channel quality information provision scheme,
where the total channel quality information feedback overhead is reduced
compared to the "Full Feedback" case described in the Technical
Background section.

[0145] Further, it should be noted that the term "resource unit" as used
herein refers to one of a plurality of resource units of a channel for
which a channel quality measure is obtained. Channel quality reporting
may thus be performed on a per-resource unit basis. Moreover, this
resource unit may or may not be equal to a resource block denoting the
smallest amount of resources of a channel that can be allocated to a user
(e.g., by scheduling). For example in an OFDMA system, a resource unit
could refer to a resource of one subframe in the time domain and a
subband in the frequency domain, while a resource block denotes a
subframe in the time domain and a subcarrier (of one of the subbands) in
the frequency domain. In another embodiment of the invention, a resource
unit refers to a range of time or frequencies (sub carriers)--in time or
frequency domain--over which the channel state is substantially flat,
e.g., a coherence time or coherence bandwidth, which may or may not be a
multiple of the respective smallest amount of resources in the
communication system (e.g., resource block, subframe, TTI).

[0146] As can be already recognized from this summary of the variables and
symbols as used herein, most of the embodiments outlined herein consider
for exemplary purposes the transmission of channel quality information
for a channel (e.g., shared channel) in communication systems. Hence,
some of the exemplary embodiments described in the sequel assume a mobile
communication system as described in the Technical Background section
above.

[0147] The invention relates to the communication of information on the
state of a channel between a transmitting entity and a receiving entity,
such as for example a mobile station and a base station in a mobile
communication system. A resource management entity preferably has some
sort of channel state information available for the link between base
station and mobile station ("downlink") as well as for the link between
mobile station and base station ("uplink"). Assuming that this resource
management entity is located within the base station or farther towards
the network side, the channel state information for the downlink may have
to be measured by the mobile station and then be transmitted via the
uplink to the base station to the resource management entity. Conversely,
if said resource management entity is located within the mobile station
or farther at the user equipment side, the channel state information for
the uplink may have to be measured by the base station and then be
transmitted via the downlink to the mobile station to the resource
management entity. In some embodiments the channel state measures (or
channel quality values) are provided or measured for each resource unit
into which the communication channel between transmitting entity and
receiving entity is divided.

[0148] One aspect of the invention is to divide the channel state measures
into distinct partitions--in case of having a channel quality measure per
resource unit this can also be viewed as a partitioning of the resource
units. Each partition consists only of a subset of the channel state
measures. The partitioning of the channel quality feedback measures may
allow for reducing the amount of overhead that needs to be attributed to
the signalling of channel quality information, as (in some embodiments)
the portioning may be advantageously used to further reduce the amount of
signalling information. Further, the partitioning of the channel quality
measures may allow for a more accurate reconstruction of the channel
state at the receiver.

[0149] Another aspect of the invention relates to the receiver that
inverts the compression scheme to reconstruct the channel quality
measures. In some exemplary embodiments of the invention, a scheduler may
utilize the information on the channel condition to schedule air
interface resources of transmitters that are served by the scheduler.
Moreover, alternatively or in addition thereto, the reconstructed channel
estimate may also be employed to determine the link adaptation to be
applied to data transmissions on a wireless channel.

[0150] A further aspect of the invention is the use of some sort of
(re)ordering scheme that is reordering the channel quality measures prior
to their transmission as channel quality information. For example, the
reordering of the channel quality measures may be obtained by an
interleaving algorithm. According to this aspect the channel quality
measures of a channel may be (re)ordered so that encoding of the measures
yields the most accurate reconstruction of the measures at the receiver.
For example, if transforming the channel quality measures and
transmitting a subset of the resulting channel quality coefficients, the
(re)ordering prior to the transformation may be chosen so as to
concentrate most power of the channel quality measures in a number of
coefficients that can be transmitted according to the encoding scheme.
The (re)ordering mechanism may be combined with the other aspects of the
invention as will be outlined in further detail in the following.

[0151] It may be advantageous but not a prerequisite that in multi-user
communication systems the channel quality feedback is most accurate for
the strongest resources. The channel quality may be periodically measured
or determined by a reporting terminal. Generally, this may, for example,
be implemented by measuring the channel quality for each of a plurality
of resource units into which the communication channel to report on is
(logically) divided at the reporting terminal to obtain a set of channel
quality values or measures (e.g., power values).

[0152] FIG. 4 shows a flow chart of a method for transmitting channel
quality information according to an embodiment of the invention. In a
first step the transmitting entity may determine 401 the channel quality
measures of the channel. This may, for example, be accomplished by
measuring a channel quality value for each resource unit of the channel
on which the transmitting entity is reporting. An exemplary channel
snapshot obtained by the measurement is shown in FIG. 14. For exemplary
purposes only it is assumed that the channel on which is to be reported
is divided into 24 resource units for which individual channel quality
measures are determined. As a result of this channel quality
determination procedure 24 channel quality values ν1, K,
ν24 are obtained.

[0153] Next, an unequal accuracy approach by creating 402 at least two
partitions of resource units is used. Each resource unit i.e., its
channel quality measure may be assigned unambiguously to exactly one
partition. The partitions may, for example, be defined such that resource
units with similar channel quality measures (e.g., power values) are
contained in the same partition.

[0154] In one exemplary embodiment, only the resource units having the
strongest channel quality values (e.g., power values) are contained in a
first partition, and other resource units are contained within a second
partition. In the example of FIG. 14, the following partitions are
created:

[0155] In this example, the partition creation is depending on e.g., one
or more partition threshold values. FIG. 14 shows an example of the
partition threshold to define a first and a second partition, each of
which contains only resource units whose SINR is either above or below
the threshold value, respectively. It is a matter of convention whether
resource units that have SINR values equal to the threshold should go
into the first or into the second partition.

[0156] Typically the partitions are each of cardinality smaller than that
of the original sequence. Without loss of generality, it may be assumed
that the number of elements in the first partition N1 is smaller
than or equal to the number of resource units in the original sequence
Nrb.

[0157] Preferably, the channel quality values of the resource units are
ordered in the same way as is the original sequence. Therefore following
the example of FIG. 14, the first partition P1 should consist of the
channel quality values with the indices 8, 9, 10, 18, 19 (i.e.,

v 8 1 , v 9 1 , v 10 1 , v 18 1 , v 19 1 ) ##EQU00008##

of the original sequence in that order, while the second partition should
consist of the channel quality values with the indices 1-7, 11-17, 20-24
of the original sequence (i.e.,

in that order. Therefore the cardinality of the first partition is five
(N1=5), and the cardinality of the second sequence is nineteen
(N2=19). The sum is therefore the cardinality of the original
sequence, twenty-four in this case (N1+N2=Nrb=24).

[0158] Evidently, when partitioning the channel quality values ν1,
K, ν24 according to this example, the sum of the number of
elements in each partition is equal to the number of resource units in
the original sequence. The partitioning (partition affiliation) of the
channel quality measures may be represented by a bitmap as illustrated in
FIG. 15, where the partition to which a respective channel quality
measure is assigned is indicated by a single bit. Obviously, more bits
per channel quality measure are needed if more than two partitions are
formed (e.g., .left brkt-top.ld(n).right brkt-bot. bits for n
partitions).

[0159] This example is also shown in FIG. 14 where a partition threshold
is used to divide the 24 channel quality measures into two partitions. As
will become more apparent from the following description, there exist
multiple schemes how to partition the channel quality measures into at
least two partitions. For example, in another embodiment, the number of
elements that should go into each partition is known before the partition
creation process. This will obviate the necessity to inform the receiver
of the number of elements that belong to a partition.

[0160] In a next step 403, the channel quality values in at least one of
the two created partitions are transformed. For example, according to one
embodiment of the invention, a discrete cosine transform for each
partition (P1 and P2) is performed. Details on a DCT as may be
used by in an embodiment of the invention may be found in Ahmed, N.,
Natarajan T. and Rao K. R., "Discrete Cosine Transform", IEEE Trans.
Computers, January 1974 incorporated herein by reference.

[0161] As a result the transformed partitions T1 and T2 are
obtained. Typically, the DCT does not change the number of elements in a
set, i.e., the cardinality of the transform is equal to the cardinality
of the source. Consequently in the example of FIG. 14, FIG. 16 and FIG.
17, the DCT of the first partition T1 contains five elements, while
the DCT of the second partition T2 contains nineteen elements, as
visualized in FIG. 16 and FIG. 17. Nevertheless, it should be noted that
it is not necessary to always calculate a number of coefficients equal to
the number of elements contained in the set to be transformed. In some
embodiments, fewer coefficients than elements in the set to be
transformed are calculated. This may, for example, be useful in an
encoding scheme where only the first M coefficients of a transformation
are transmitted.

[0162] In step 404, the channel quality coefficients obtained by the
transformation in step 403 are encoded. In one exemplary embodiment of
the invention, this may be accomplished by performing a compression of
the coefficients for each transformed partition Ti separately.

[0163] For example, in each transformed partition only certain DCT
coefficients are selected for feedback transmission. Generally, the
number of DCT coefficients selected for transmission Mi is dependent
on the partition number i. In the example shown in FIG. 16 and FIG. 17,
these numbers have been chosen as M1=M2=3.

[0164] Alternatively, compression may take the coefficients of at least
two transformed partitions into account. In this example, the total
number of DCT coefficients to be transmitted after compression (e.g., the
sum M1+M2 for two partitions) is a (pre)determined or
preconfigured value.

[0165] Alternatively, compression may take the number of available bits
for channel quality information transmission of at least two transformed
partitions into account. In this example, the total number of available
bits for the channel quality information transmission compression after
compression is a (pre)determined or preconfigured value. The number of
transmitted DCT coefficients after compression per partition may then be
determined taking the required signalling for at least two partitions
into account, plus the necessary amount of bits for partition affiliation
or coefficient index signalling, if required. A similar approach may also
be used when "directly" compressing the channel quality values, i.e.,
when not performing a transformation of the partition(s).

[0166] The mobile terminal may determine how many DCT coefficients from
each transformed partition are selected for transmission and under which
constraint(s) the selection is performed. If, for example, the values
within a transformed partition are constant or nearly constant, then one
or two DCT coefficients are sufficient for reconstruction at the
receiver. Consequently the mobile station may transmit more DCT
coefficients of another partition that shows greater fluctuations in its
DCT coefficients.

[0167] Since the transmitter, e.g., the mobile station, has the most
accurate channel information, it may deliberate within the above
constraints, depending on the actual channel conditions, how to use the
available number of coefficients or bits to convey the optimum accuracy
to the receiving entity. The constraints could be further defined to
require a minimum number of coefficients for a given partition, limiting
the degree of freedom of the mobile terminal. This method may however
require additional signalling of the selected coefficients from the
mobile station to the receiving entity.

[0168] In one embodiment of the invention, the coefficients are chosen
according to their absolute values or according to their squared absolute
value. In another embodiment, the coefficients are chosen such that in
each partition the selected coefficients contain at least a threshold
amount of power of the whole partition. In an example, since the first
(transformed) partition T1 may be more important than the second
(transformed) partition T2, it may be beneficial to select as many
coefficients from the first partition T1 so that the selected
coefficients contain more than a partition threshold value of
Pthreshold e.g., more than Pthreshold=99%, of the total power
contained in the first partition T1. If more coefficients are
required for this criterion than available in the first partition
T1, the strongest coefficients of partition T1 should be
selected. If fewer coefficients than available are required for this
criterion, then the remaining coefficients may be employed to select an
appropriate number of coefficients from the second partition T2.
Obviously, other constraints like those mentioned above (e.g., minimum
number of selected coefficients per partition) may further reduce the
degree of freedom.

[0169] For example, the DCT coefficients for the first partition T1
according to FIG. 16 (obtained by squaring and normalization)
respectively contain 98.07%, 0.41%, 0.02%, 0.5%, and 1% of the total
power. Consequently to capture more than 99% of the power, the selection
of coefficients 1 and 5 (i.e., c11 and c51) of
partition T1 may be sufficient. Assuming that a total number of 6
coefficients can be selected for transmission in the encoding procedure
404, the remaining 4 coefficients can then be selected from the second
partition (see FIG. 17). To save signalling for the second partition, the
first four coefficients of the second partition T2 may be selected
by default. For higher accuracy, the four strongest coefficients of
partition T2 may be selected. In this fashion, coefficients 1, 3,
10, and 11 (i.e.,

c 1 2 , c 3 2 , c 10 2 , and c 11 2 ) ##EQU00010##

may be selected in the example. These coefficients contain almost 88% of
the power of partition T2.

[0170] Without using this threshold power criterion for selecting the
coefficients from the transformed partitions for transmission, the power
contained in the selection for partition T1 is 99.57% (i.e., a gain
of 0.5%), while for partition T2 it is only roughly 85.38% (i.e., a
loss of about 2.5%) given that three strongest coefficients from each
partition are chosen. Depending on the constraints imposed by the
communication system, those skilled in the art will be able to select the
most suited coefficients from the partitions as needed.

[0171] Next, in step 405 the selected channel quality coefficients from
the partitions are transmitted as channel quality information to the
receiving entity. Depending on the encoding scheme it may also be
necessary to encode information indicating the partitioning (partition
affiliation) of the channel quality values at the transmitter, for
example, by means of a bit pattern as shown in FIG. 15. Further, if no
preconfigured coefficients from the partitions are selected it may be
necessary to further inform the receiver which coefficients are
communicated by signalling the indices of coefficients (coefficient index
signalling) included in the channel quality information.

[0172]FIG. 5 shows another exemplary flow chart of a method for
transmitting channel quality information according to an embodiment of
the invention. Essentially, the flow chart shown in FIG. 5 is similar to
same in FIG. 4. In contrast to the scheme outlined with respect to FIG. 4
above, the channel quality information transmission scheme shown in FIG.
5 does not include a transformation of the partitions P1 and P2
prior to encoding. Instead, the channel quality values νi of the
respective partitions may be directly encoded 501 using similar
mechanisms as described with respect to FIG. 4 above and are subsequently
transmitted 502 as channel quality information to the receiver.

[0173] Next the reconstruction of the channel quality information at the
receiving entity will be discussed with respect to FIG. 6 and FIG. 7.
FIG. 6 shows an exemplary flow chart of a method for receiving and
reconstructing channel quality values for channel quality information
according to an embodiment of the invention.

[0174]FIG. 6 essentially mirrors the steps of FIG. 4 at the receiving
entity. First, the channel quality information provided by a transmitter
(e.g., a mobile station) is received 601 at the receiver such as a base
station having scheduling and/or link adaptation functionality. The
channel quality information may then be decoded 602. This means that the
channel quality coefficient values (and optionally the indices for the
signalled channel quality coefficient values) in the channel quality
information are used to first reconstruct the channel quality
coefficients that have been selected by the transmitter for transmission
in terms of their values and position.

[0175] Further, the partitions Ti may be reconstructed 603 based on
the partitioning pattern (partition affiliation) in the channel quality
information received from the transmitter. Thereby the respective
coefficients in the partitions may be either set according to the
signalled coefficient values or to zero (or a predetermined value) if a
coefficient value is not signalled in the channel quality information.

[0176] Upon having reconstructed the partitions Ti same may be
transformed 604 to reconstruct partitions Pi of channel quality
values. The partitions Pi of channel quality values are subsequently
combined to reconstruct the set of channel quality measures ν1,
K, ν24 at the receiver for the plurality of resource units.

[0177] FIG. 7 shows another exemplary flow chart of a method for receiving
and reconstructing channel quality values for channel quality information
according to an embodiment of the invention. Essentially, the individual
steps shown in FIG. 7 are similar to those shown in FIG. 6. However, as
in FIG. 5, it is assumed that the channel quality values of the
partitions Pi are directly encoded and transmitted to the receiver.
Hence, upon the reception of the partitions Pi of channel quality
values may be directly reconstructed 702 from the channel quality
information by a decoder in step 701.

[0178] FIG. 20 shows the channel state as in FIG. 14 and a reconstruction
of channel quality values from compressed partition-wise DCT according to
an exemplary embodiment of the invention. The partitioning of the channel
quality values in two partitions and the partition-wise encoding of
channel quality coefficients by selecting M1=M2=3 coefficients
from each partition allows for an accurate reconstruction of the original
sequence of channel quality measures. It is especially worth noting that
for the most important resource units (i.e., those having the highest
channel quality values) the reconstruction is very accurate.

[0179] The reason for the accurate reconstruction of the channel quality
values from the channel quality information at the receiver when using
one of the schemes according to the different embodiments of the
invention will be outlined in the following with respect to FIG. 22 to
FIG. 27.

[0180] FIG. 22 shows an example of an original sequence consisting of only
two distinct SINR values, and the corresponding DCT transform. It should
be noted that the presence of only two distinct channel quality values in
this example is only intended to illustrate the benefits of employing the
present invention. As can be seen from the DCT transformation of the
original sequence of channel quality values, there is a strong DC
component and several higher-index DCT coefficients representing a
substantial part of the power of the original sequence. Hence, the number
of coefficients to represent a given power threshold value of
Pthreshold=99% is significant and still implies a significant
overhead.

[0181] Partitioning the channel quality values shown in the upper part of
FIG. 22 into two partitions in this example allows for having a more
regular distribution of channel quality values in each of two partitions.
Comparing the exemplary original sequence of channel quality values as in
FIG. 22, two partitions may be created that comprise channel quality
values of resource units with values of 4 and 1, respectively.
Consequently the first partition contains only elements of having a
channel quality value equal to 4 as shown in FIG. 24 upper part (i.e.,
elements ν1, ν2, ν4, ν6, ν8,
ν9, ν11, ν13, ν15, ν18,
ν21 of the original sequence), while the second partition
contains only elements having a channel quality value equal to 1 as shown
in FIG. 26 upper part (i.e., elements ν1, ν3, ν5,
ν7, ν10, ν12, ν14, ν16,
ν17, ν19 ν20, ν22 to ν24 of the
original sequence). The partitioning may either be achieved by defining
that the first partition should contain 10 elements and the second
partition 14 elements, or a partition threshold of a value between 1 and
4 may have been defined.

[0182] As can be seen from FIG. 24 and FIG. 26, the distribution of
channel quality values in each of the partitions is more regular in
comparison to the original sequence shown in FIG. 22. Due to this more
regular distribution of the channel quality values in the two partitions
(in this example a uniform distribution is obtained), the power of the
DCT coefficients of each of the two partitions shown in FIG. 24 and FIG.
26 in the lower part, respectively, may be concentrated in the first
coefficients of the DCT transform. In this example, due to the uniform
distribution of the values in each partition, the total power of the
channel quality values of a partition concentrates in the DC component of
the DCT transform as can be also seen from the bitmaps indicating the
strongest coefficients shown in FIG. 25 and FIG. 27 respectively.

[0183] This effect allows in turn reducing the number of coefficients that
need to be transmitted. In the example, it is sufficient to transmit the
value of the DC component of the DCT transform (i.e., the first
coefficient) of each partition as well as information on the partitioning
(partition affiliation) of the values/coefficients (and optionally the
index of the transmitted DC component in the respective partition) to
allow for an ideal reconstruction of the original sequence of the channel
quality values of FIG. 22 at the receiver. Thereby, the overhead for
transmitting these channel quality information to the receiver may be
less than in prior-art schemes.

[0184] In the subsequent sections several issues relating to the invention
according to one of the different embodiments will be discussed in the
following.

Transformation Scheme/Encoding Scheme

[0185] In the previous sections, it has been suggested to facilitate a
better compression of the information to transmit by applying the DCT
transform to the data in the individual partitions. Due to the nature of
the constituent cosine waveform, the use of a DCT may, for example, be
particularly applicable when the data in the partitions is of continuous
nature or in cases of discrete nature of the data, if the discrete values
do not show large differences to each other. According to another
embodiment, also other transformation schemes may be employed, such as,
for example, the Fourier transform or other related continuous functions.
Further, also other transform functions may be used, such as the Haar
transform, Hankel transform, Daubechies wavelet, etc. Use of the latter
transforms may be advantageous, for example, in case of a more discrete
nature of the data in the partitions (as it might be the result of a
coarse quantization of the channel quality values or a result of mapping
of the channel quality values onto modulation and coding scheme (MCS)
indices). Those skilled in the art will recognize that the optimum
compression transformation function will depend on the nature and
properties of the data that is to be compressed.

[0186] In most embodiments of the invention discussed previously herein,
all partitions have been encoded or compressed using the same
encoding/compression scheme. Alternatively, each partition may employ a
compression scheme independently from any other partition. For example, a
first partition may be compressed employing the discrete cosine
transform, while another partition may be compressed using a Daubechies
wavelet. From an implementation aspect however, it may be advantageous to
employ the same compression approach in all partitions, so as to minimize
the hardware or software efforts necessary.

[0187] Further according to another embodiment of the invention it may be
beneficial not to transform the channel state measures prior to encoding,
but--for at least one partition--to compress the values directly by
transmitting only a subset of the values in a partition. This may lead to
a kind of "Best M" compression, as outlined in the Technical Background
section, however, on a partition-basis.

[0188] It should be noted that the choice of transform or encoding schemes
or parameters for at least one partition may vary over time. An option to
determine the transform or encoding scheme or parameters for at least one
partition may take the channel quality information reporting frequency
into account. For example, if channel quality information reporting
occurs infrequently (e.g., at a rate below a threshold frequency), it may
be advantageous to transmit a large number of values/coefficients to
allow very detailed reconstruction, or alternatively to choose an
encoding scheme that offers a high amount of accuracy such as "DCT
Strongest M" or "Best M Individual".

[0189] In contrast, if channel quality information reporting occurs
frequently (e.g., at a rate equal to or above a threshold frequency),
each channel quality information signal (message) may preferably be
rather small, so as to keep the overall required amount of signalling
small. This may result in the choice of a few number of
values/coefficients or in the choice of a quite coarse encoding scheme
like "Average", "Best M Average", or "DCT First M".

[0190] In another embodiment, for a given first channel quality
information reporting frequency, a first transform or first encoding
scheme or first set of channel quality information transmission
parameters (such as number of transmitted values/coefficients, number of
partitions, number of values in a partition, partition threshold values,
etc.) is used. For channel quality information reports between two such
channel quality information reports, a second transform or second
encoding scheme or second set of channel quality information transmission
parameters is used.

[0191] Similarly, also in case the channel state changes significantly
between successive reports (e.g., the difference between the total energy
of one or a plurality of channel quality measures at two time instants is
above a threshold) the transmitter may decide to transmit a large number
of values/coefficients to allow very detailed reconstruction, or
alternatively to choose an encoding scheme that offers a high amount of
accuracy.

Reordering

[0192] As outlined above, another aspect of the invention is the
(re)ordering of channel quality values, for example, in combination with
using an encoding scheme employing a transformation of the channel
quality values. FIG. 29 and FIG. 30 show exemplary flow charts of a
method for transmitting channel quality information using (re)ordering
mechanisms according to different embodiments of the invention. While the
embodiment shown in FIG. 29 does not employ partitioning and transforming
the channel quality values, the embodiment shown in FIG. 30 further
includes steps to transform the (re)ordered channel quality values prior
to transmission. It should be noted that in both embodiments, also a
partitioning of the channel quality values prior to or after (re)ordering
may be foreseen.

[0193] As in FIG. 4 and FIG. 6, the channel quality values ν1, ,
νNrb indicative of the channel quality may be either first
measured 2901 or may be available at the transmitter. Next, the channel
quality values may be (re)ordered 2902 to obtain a sequence of
(re)ordered channel quality values ν1', , ν'Nrb.
Subsequently, in the embodiment illustrated in FIG. 29, the (re)ordered
channel quality values are encoded 2903 using one of the compression
schemes described herein. In the embodiment shown in FIG. 30, the
(re)ordered values may be transformed 3001, for example, using a DCT
transformation as explained above first and are subsequently encoded 3002
using one of the compression schemes described herein. The resulting
channel quality information is subsequently reported 2904, 3003 to the
receiver.

[0194] The reordering in step 2902 may be done according to various
different mechanisms. For example, a known (re)ordering mechanism may be
applied that is also known to the receiver. This would obviously require
no additional signalling overhead.

[0195] In another embodiment of the invention, a limited number Nr,
of (re)ordering mappings are determined, for example, by means of
applying interleaving scheme(s) in a trial-and-error fashion. The
transmitter may obtain the reordered sequences of channel quality values
using each of the defined (re)ordering algorithms prior to
transformation, thus obtaining Nr reordered sequences. Out of these
sequences, the transmitter may choose one (re)ordered sequence for
transmission (e.g., after transformation and selection of the
coefficients/values) that fulfils a certain optimality criterion. Such an
optimality criterion may, for example, be the maximum amount of power
contained in the first M coefficients or values in the reordered
partition. Another optimality criterion may be the mean square error
between the reconstructed sequence of channel quality values and the
(measured) original sequence of channel quality values. This criterion
would however imply higher transmitter complexity, as the transmitter may
need to reconstruct the sequence to determine the mean squared error for
choosing the optimum (re)ordering scheme or parameters. This operation of
the transmitter may also be considered an iteration of testing the
resulting compressed information against an optimality criterion as
described above.

[0196] In this exemplary embodiment, the (re)ordering signalling merely
needs to indicate which out of the Nr defined (re)ordering schemes
has been selected. This may only require .left
brkt-top.ld(Nrb).right brkt-bot. bits for the (re)ordering signal.
Another option would be to define the (re)ordering mapping by at least
one reordering parameter and to vary this parameter(s), for example,
within a given range of parameter values, so as to obtain the
(re)ordering fulfilling a certain optimality criterion. In this
variation, only the at least one reordering parameter may be signalled.
This may, for example, be realized in a fashion similar to that outlined
below for the signalling of the partitioning and coefficients.

[0197] It may be noted that the (re)ordering may be applied to the channel
quality values before transformation of values to coefficients, or it may
be applied to the channel quality coefficients obtained after
transformation of the channel quality values. For example, in FIG. 30,
the order of functional blocks 2902 and 3001 may be exchanged. Either way
the optimality criterion is preferably tested after both the (re)ordering
and transformation have been applied.

[0198] The (re)ordering of the channel quality values may also be employed
together with the concept of partitioning. In one embodiment of the
invention, the channel quality values may be (re)ordered prior to their
partitioning. In another embodiment of the invention the values or
coefficients within a partition may be reordered prior to their
transformation or encoding, respectively. This may be particularly
beneficial if a compression scheme is employed that is most accurate for
small data indices. A further advantage of reordering the channel quality
values in a partition may be that the reordering allows achieving a more
regular distribution of channel quality values in a partition, which in
turn yields that most power of the reordered partition values may be
found in only a very low number of coefficients of the DCT transform.
Hence, according to one embodiment, the reordering is performed such that
the reordered partition has a more regular distribution of channel
quality values than the original partition prior to reordering. The
(re)ordering may be, for example, a sorting or shifting of channel
quality values in a partition. Those skilled in the art will perceive
that the method of (re)ordering may be in some way known to the receiver
e.g., by signalling or convention.

[0199] Generally, the (re)ordering of the data may be signalled to the
receiver as well in the channel quality information, unless the
(re)ordering algorithm is known a priori (e.g., using a fixed permutation
pattern) to both the transmitter and the receiver. Allowing for an
arbitrary (re)ordering may impose heavy demands on the amount of bits
that need to be signalled to indicate the reordering applied to the data.

[0200] Hence, according to one embodiment of the invention one out of a
limited number Nr of (re)ordering mappings (e.g., using
interleavers) that are employed by the transmitter is determined (e.g.,
in a trial-and-error fashion). For example, the transmitter may obtain
data reordered partitions using each of the defined (re)ordering
algorithms prior to transformation, thus obtaining Nr reordered
partitions. Out of these, the reordered partition may be chosen for
transmission (after compression of the coefficients/values) that fulfils
a certain optimality criterion. As mentioned above, such an optimality
criterion could be the maximum amount of power contained in the first M
coefficients or values in the reordered partition. In this exemplary
embodiment, the (re)ordering signalling merely needs to indicate which
out of the Nr defined (re)ordering schemes has been selected. This
may only require .left brkt-top.ld(Nrb).right brkt-bot. bits for the
(re)ordering signal.

[0201] Another optimality criterion may be the minimal variance or minimum
mean square error when comparing the original channel quality values with
the reconstructed channel quality values from the reordered partition. In
this exemplary embodiment, the (re)ordering signalling merely needs to
indicate which out of the Nr defined (re)ordering schemes has been
selected. This may only require .left brkt-top.ld(Nrb).right
brkt-bot. bits for the (re)ordering signal.

[0202] According to another embodiment of the invention, an interleaver or
(re)ordering algorithm is used to generate a number of Nr
interleaves or (re)ordering realizations by using at least one variable
interleaver or (re)ordering parameter. The particular choice which out of
the Nr interleaver or (re)ordering realizations is employed by the
transmitter to transmit the channel quality information is determined
e.g., in a trial-and-error fashion according to an optimality criterion
as above, mutatis mutandis. In this embodiment, the transmitter merely
needs to indicate the at least one employed interleaver or (re)ordering
parameter value for the selected interleaver or (re)ordering mapping
indicating the permutation/interleaving of the input sequence.
Alternatively, the transmitter merely needs to indicate which out of the
Nr generated realizations has been selected.

[0203] The (re)ordering approach may, for example, be particularly
advantageous if a "First-M DCT" scheme or similar low-index compression
schemes is employed to encode the channel quality values of a partition.

Partitioning of the Channel Quality Values

[0204] In most embodiments having been discussed so far, a partitioning
according to the channel quality values on a resource unit basis has been
used. However other classifications can also be used to create the
partitions. In one embodiment, the partitioning is based upon what
modulation and coding scheme may be supported by a resource unit at a
given target error rate. In another embodiment, the partitioning is based
on the variation of the channel within a resource unit, such that
resource units with nearly constant channel are grouped in one partition,
and resource units with a fluctuating channel are grouped in a second
partition. In another embodiment, a combination of classification
criteria mentioned is used to create the partitions.

[0211] To signal the assignment of a respective resource unit to a
respective partition, i.e., the partition affiliation, the following
methods may be used: [0212] In one example, a map of a size equal to
the number of resource units is transmitted, each map element
representing a resource unit index, where e.g., a first value (e.g., "0")
signifies assignment to a first partition, and a second bit value (e.g.,
"1") signifies assignment to a second partition. In case of only two
partitions, the map is preferably constructed as a bitmap. Otherwise for
each map element multiple bits may be required. The bitmap is exemplified
in FIG. 15 as already indicated above. [0213] Another exemplary method is
the use of a combination index. For a number of resource units Nrb,
and a number of resource units assigned to a first partition N1,
there exist only

[0213] ( N rb N 1 ) ##EQU00011##

combinations of possible assignments. Therefore it is sufficient to
signal which of these

( N rb N 1 ) ##EQU00012##

(combinations is transmitted. This requires

ld ( N rb N 1 ) ##EQU00013##

bits. In case of only two partitions, it is sufficient to signal the
assignment of resource units to one partition, as the remaining resource
units automatically belong to the other partition. To reduce the
signalling in this case, it may be advantageous that the signalling is
done for the partition that contains fewer resource units.

Partition Value/Coefficient Signalling

[0214] As indicated above, if not using an encoding scheme where the
indices of the signalled channel quality coefficients or values are known
to the receiver a priori, it may be necessary to signal the indices of
the transmitted coefficients or values. For each partition, the indices
of the signalled coefficients or values may be signalled in the following
fashions: [0215] A bitmap of a size equal to the size of the partition
may be transmitted, each bit representing a value/coefficient index,
where a first bit value (e.g., "0") signifies no transmission of the
respective value/coefficient, and a second bit value (e.g., "1")
signifies transmission of the respective value/coefficient. This method
imposes no a priori restriction on the number of values/coefficients to
be transmitted. This solution is exemplified in FIG. 13, FIG. 18, FIG.
19, FIG. 23, FIG. 25 and FIG. 27. [0216] Combination Index; assuming that
the number of transmitted coefficients Mp and the total number of
coefficients in a partition M0 are known, there exist (basic
statistics) only

[0216] ( M 0 M p ) ##EQU00014##

combinations of possible coefficient transmissions. Therefore it is P
sufficient to signal which of these

( M 0 M p ) ##EQU00015##

combinations is transmitted. This requires

ld ( M 0 M p ) ##EQU00016##

bits. This may be done for each partition individually. The approach may
P be applied to transmitted values instead of transmitted coefficients
mutatis mutandis. [0217] The coefficients are signalled for both
partitions jointly; There can be a bitmap equal to the number M0 of
coefficients for all partitions, where the first M1 bits represent
the coefficient indices of the first partition, and the final M2
bits represent the coefficient indices of the second partition
M1+M2=M0. A first bit value (e.g., "0") signifies no
transmission of the respective coefficient, and a second bit value (e.g.,
"1") signifies transmission of the respective coefficient. This approach
may be applied to values instead of coefficients mutatis mutandis. [0218]
Also for signalling the coefficient indices a combination index may be
used. The coefficients may, for example, be signalled for both partitions
jointly; assuming that the total number of transmitted coefficients for
all partitions together is Ms and the total number of coefficients
for all partitions M0 are known, there exist only

[0218] ( M 0 M s ) ##EQU00017##

index combinations of possible coefficient transmissions. Therefore it is
sufficient to signal which of these

( M 0 M s ) ##EQU00018##

index combinations is transmitted. This requires

ld ( M 0 M s ) ##EQU00019##

bits. This approach may be applied to values instead of coefficients
mutatis mutandis. [0219] In all of the above options, any DC component
of any partition may be exempted from signalling if it is always
transmitted. Persistent transmission of the DC component may be
advantageous since this is equivalent to the average power level within a
partition. With the numerology defined above, e.g., instead of

[0219] ld ( M 0 M p ) , only ld (
M 0 - 1 M p - 1 ) ##EQU00020##

bits are necessary for the coefficient index signalling. Similarly other
indices may be designated a priori for persistent transmission, up to the
extreme that always the identical coefficient indices are transmitted.
Obviously in the latter case there is no need for signalling the indices
for such a partition. Generally this may be done separately for each
partition, or for the indices of all partitions, so that there would be
no index signalling at all.

[0220] Assuming that there are two partitions, and that the signalling for
the assignment to partitions (partition affiliation) as well as for the
transmitted coefficient indices uses a combination index, respectively,
and furthermore assuming that the DC component for each partition is
always transmitted, we may calculate the number of required bits for
signalling for the proposed scheme as

where for clarity reasons the partition affiliation and value/coefficient
index fields are separated. If these are combined into a single index
field, some bit(s) may be saved additionally, as the number of required
bits may then be calculated as

[0221] As identified previously, the signalling of the value/coefficient
indices typically makes up a non-negligible part of the required
signalling. Therefore it may be advantageous to use only a single
value/coefficient index signal field that is valid for more than one
partition.

[0222] In the example of FIG. 16 and FIG. 17, it has been determined that
for the first partition, three coefficients should be chosen for
compressing the coefficients of partition T1, and the same number of
coefficients for partition T2. Considering the "strongest" criterion
for partition T1, coefficients

c 1 1 , c 4 1 , and c 5 1 , ##EQU00023##

should be chosen for transmission, as also shown in FIG. 18. In order to
save the signalling for the coefficients of partition T2, the
coefficients at the same indices may be chosen for transmission, i.e.,
coefficients

c 1 2 , c 4 2 , and c 5 2 . ##EQU00024##

Obviously these coefficients may generally not be the strongest
coefficients of partition T2. In principle the choice of what
coefficients are transmitted may be based on any partition. In one
embodiment, the coefficients are chosen so as to represent the strongest
coefficients in the partition representing the strongest resource units.
In another embodiment, the choice of coefficients is based upon the
coefficient-wise average magnitude of at least two partitions.

[0223] In case that there is not an equal number of coefficients for the
partitions, a coefficient for a non-existent index in a partition may be
set to a "virtual" zero for the purposes of reduced signalling. For
example, if coefficient c10 had been chosen for transmission of both
partitions, the value transmitted for partition T1 should be zero,
as the transform for partition one contains only 5 coefficients. Likewise
if averaging is used according to one of the mentioned embodiments, a
coefficient for a non-existent index in a partition may be set to a
"virtual" zero for the purposes of determining the coefficient-wise
average magnitude of at least two partitions.

[0224] The effect of the reduced coefficient signalling, using the same
coefficients for partition T2 as for partition T1, can be seen
in FIG. 21. FIG. 21 illustrates the channel state as in FIG. 14 and a
reconstruction of channel quality values from compressed partition-wise
DCT with reduced coefficient signalling overhead according to an
exemplary embodiment of the invention. The reconstruction of the channel
quality values based on a reduced amount of channel quality information
shows larger deviations from the true channel than the reconstruction
including the full partition coefficient signalling. However the saving
in signalling information may justify this loss.

[0225] Table 2 below illustrates the channel quality values of the channel
as well as the reconstructed channel quality values using an encoding
scheme as suggested with respect to FIG. 14, FIG. 16 and FIG. 17 as well
as the reconstructed channel quality values using an encoding scheme as
suggested with respect to FIG. 14, FIG. 16 and FIG. 17 and in addition
reducing the signalling information further, by signalling the
coefficients of partition T2, the coefficients at the same indices
may be chosen for transmission for partition T1, i.e., coefficients

c 1 2 , c 4 2 , and c 5 2 ##EQU00025##

as discussed above. A graph of the numerical values is shown in FIG. 20
and FIG. 21 respectively.

[0226] As can be recognized from the table both compression schemes allow
for a very accurate reconstruction of the channel quality values for the
strongest coefficients of the real channel state. The suboptimum choice
of the channel quality coefficients for signalling for the second
partition in the reduced signalling scheme in the right column is mainly
reflected in the less accurate reconstruction of channel quality values
of low power (e.g., for indices 11 to 17). However, these low power
measures are typically less relevant, as same should be not be chosen for
data transmission by the respective transmitter (i.e., should not be
assigned to the terminal for transmission).

[0227] It should be noted that the reduced signalling approach outlined
here for partition coefficients may be applied to partition values
mutatis mutandis.

[0237] It should be obvious to those skilled in the art that the
expression that is used widely in the detailed description about
"strongest resource units" etc. is referring to a Signal-to-Noise ratio
or a Signal-to-Interference ratio or a Signal-to-Noise-plus-Interference
ratio, or generally any measure that relates to a signal strength.
However the interpretation for other measure mentioned above can be
adapted mutatis mutandis. For example, a strong Signal-to-Interference
ratio may also be expressed as a modulation scheme indicator that
indicates a high-order modulation scheme (e.g., 16-QAM, 64-QAM, etc.), or
as a coding scheme indicator that indicates a weak coding scheme (e.g.,
by a high coding rate), and so forth. Those skilled in the art will
readily be able to derive the corresponding interpretations for other
measures or combinations of any measures.

[0244] The following examples of transmission technologies should provide
additional understanding to those skilled in the art how to beneficially
employ the invention.

[0245] In an FDM(A) transmission scheme, Nrb data resources are
available in frequency domain. Therefore also the channel quality measure
may be obtained as a frequency-domain variable of Nrb values. A
first partition may consequently contain those frequency resource blocks
with the M1 strongest channel quality measures, while a second
partition contains the remaining M2 channel quality measures. It may
be noted that this approach may also be used in the special case of
OFDM(A), as it can be seen as a special instance of an FDM(A)
transmission.

[0246] In a multi-antenna transmission scheme, the channel quality value
may vary from one antenna to the other. Those skilled in the art will
recognize that this is valid both for transmit and receive antennas. In
particular with respect to MIMO technologies, the communication system
will generally consist of NMIMO MIMO data streams, for each of which
a plurality of channel quality measures may be obtained if e.g., each
stream uses an FDM transmission scheme. Consequently a first partition
may contain the channel quality measures valid for a first MIMO data
stream, while a second partition may contain the channel quality measures
for a second MIMO data stream.

Number of Partitions

[0247] Most exemplary embodiments relate to the concept of partition-wise
compression using two distinct partitions. However the concepts presented
can easily be extended into an arbitrary number of partitions.

Hierarchical Partitioning

[0248] In another embodiment of the invention not only the original
sequence of channel quality values may be partitioned, but also the
resulting partitions may be again divided into sub-partitions. Generally,
a first partitioning is made to create partitions Ai. In a second
time instant, the data from at least one of said partitions Ai is
further partitioned to create partitions Bi,j. In this way, i
denotes the index of the parent partition, while j denotes the index of
the child partition belonging to parent partition i. Compression may be
employed in any of the parent or child partitions according to any of the
methods outlined in the present invention. This may be used to further
increase the granularity and accuracy of the compression and
reconstruction.

[0249] It may be noted that such hierarchical partitioning may be
beneficially employed in a MIMO case. As mentioned above, a first
partition A1 may contain the channel quality measures valid for a
first MIMO data stream, while a second partition A2 may contain the
channel quality measures for a second MIMO data stream. Then a first
sub-partition B1,1 may contain the strongest channel quality
measures contained in partition A1, while a second sub-partition
B1,2 may contain the remaining channel quality measures contained in
partition A1. This can be applied mutatis mutandis to partition
A2 and sub-partitions B2,1 and B2,2.

Transmission of Channel Quality Information

[0250] In another embodiment of the invention, the encoded and/or
compressed data of all partitions may be transmitted at the same time.
However, other solutions may be possible, as outlined in the following.

[0251] For example, also a partition-wise successive (serial) transmission
of the encoded channel quality information is possible. At a first time
instance, the channel quality information for a first partition is
transmitted. At a second time instance, the channel quality information
for a second partition is transmitted. The order may be predetermined,
signalled, or determined according to e.g., a deviation criterion:
channel quality information is transmitted for that partition, for which
there occurs the biggest change compared to the previous transmitted
compressed data for that partition.

[0252] Another option is the use of a successive (serial) transmission of
the encoded channel quality information components. At a first time
instance, a first coefficient of the channel quality information is
transmitted. At a second time instance, a second coefficient of the
channel quality information is transmitted. This may be employed
partition-wise (i.e., the coefficients for a first partition are
transmitted before the coefficients for a second partition), or in a
round-robin or similar fashion (i.e., a first coefficient is transmitted
for a first partition, followed by a first coefficient for a second
partition, followed by a second coefficient for the first partition,
etc.).

[0253] Another option is the use of a successive (serial) transmission of
the encoded channel quality information components. At a first time
instance, for example, the partition affiliation signal is transmitted,
while the value/coefficient signal for the at least one partition is
transmitted at an at least second time instance.

[0254] A further option is to update channel quality information.
According to one embodiment, only the difference of the channel quality
information for a partition between a first transmission instance and a
second transmission instance is transmitted. Said difference may either
refer to the transmitted channel quality information at said first
transmission instance, or refer to the combination of several previously
compressed data transmission instances.

[0255] Another option to transmit the encoded channel quality information
according to a further embodiment of the invention may be a
partition-wise update/transmission interval. For a first partition,
advantageously one that consists mainly of strong resource units, the
channel quality information is transmitted using a first
update/transmission interval. For a second partition, the channel quality
information is transmitted using a second update/transmission interval.
Preferably the first update/transmission interval is shorter than the
second update/transmission interval.

[0256] It should be noted that the aforementioned transmission options in
time domain can be easily extended or changed to frequency domain, code
domain, antenna domain, polarization domain, etc. mutatis mutandis.

[0257] Further, as already briefly mentioned above it is to be noted that
the concepts of the invention outlined in various exemplary embodiments
herein may be advantageously used in a mobile communication system as
described in the Technical Background section that may, for example, have
an architecture as exemplified in FIG. 28. The mobile communication
system may have a "two node architecture" consisting of at least one
Access and Core Gateway (ACGW) and Node Bs. The ACGW may handle core
network functions, such as routing calls and data connections to external
networks, and it may also implement some RAN functions. Thus, the ACGW
may be considered as to combine functions performed by GGSN and SGSN in
today's 3 G networks and RAN functions as, for example, radio resource
control (RRC), header compression, ciphering/integrity protection and
outer ARQ. The Node Bs may handle functions as, for example,
segmentation/concatenation, scheduling and allocation of resources,
multiplexing and physical layer functions. For exemplary purposes only,
the NodeBs are illustrated to control only one radio cell. Obviously,
using beam-forming antennas and/or other techniques the NodeBs may also
control several radio cells or logical radio cells. Further, a MIMO
transmission scheme may be utilized in the communication with the
different mobile stations or terminals.

[0258] In this exemplary network architecture, a shared data channel may
be used for communication on uplink and/or downlink on the air interface
between mobile stations (UEs) and base stations (NodeBs). This shared
data channel may have a structure as shown in FIG. 1 and/or may be viewed
as a concatenation of subframes as exemplarily illustrated in FIG. 2 or
FIG. 3. According to an exemplary embodiment of the invention, the shared
data channel may be defined as in the Technical Background section herein
or as in 3GPP TR 25.814, available at http://www.3gpp.org and
incorporated herein by reference.

[0259] In the embodiments of the invention described herein, the
information on the channel state may be used to communicate a "snapshot"
of the channel quality at a given time instance or over a time interval.
If information on the channel state should be used for scheduling or link
adaptation, a short report interval may be advantageous. However, even if
the report interval of the channel state information is not minimal, the
receiver could utilize the information on the channel state in the past
for the prediction of a future channel state, which may allow for an
adequate scheduling and/or link adaptation.

[0260] In some embodiments of the invention, the receiver (e.g., Node B in
FIG. 28) of the information on the channel state may also comprise a
scheduling for scheduling the mobile stations and/or a link adaptation
entity for performing link adaptation on the communication channel. The
mobile terminals served by a base station (i.e., the receiver in this
example) may receive information on the channel state from the mobile
stations to facilitate scheduling and/or link adaptation.

[0261] It should be noted that, particularly in a mobile communication
system, the transmitted channel quality information may need to be
protected against errors. To this end, one or more of well-known
techniques like error detection coding (e.g., CRC checksum), forward
error correction (Convolutional code, turbo code, Reed-Solomon code),
automatic repeat requests (ARQ), etc. may be employed prior to
transmission of the encoded channel quality information. Obviously same
techniques should be processed appropriately in the receiver after
reception prior to decoding of channel quality information.

[0262] Moreover, it should be noted that in another embodiment of the
invention any parameter used to control one or more aspects of the
partitioning, transformation or encoding may be determined by a network
management entity, e.g., a NodeB. In this case, the respective control
parameters may be signalled from the network to the channel quality
information transmitter (e.g., a mobile station) using control
signalling, e.g., Layer 1/Layer 2 (L1/L2) control signals on a L1/L2
control channel, control information in a MAC header, or using RRC
signalling. The frequency of such L1/L2 control signalling for CQI
parameters may be periodic or event-driven. The frequency of the control
signalling may be determined by a management entity. It may be
additionally advantageous to convey different control parameters using
control signalling in different resources, e.g., using resources that
differ in at least one of: [0263] Time unit (e.g., different timeslot,
resource block, radio frame, subframe, transmission time interval,
millisecond, etc.) [0264] Frequency unit (e.g., different carrier
frequency, subband, resource block, etc.) [0265] Antenna unit (e.g.,
different transmit antenna, receive antenna, antenna array unit, MIMO
channel, etc.) [0266] Code unit (e.g., different spreading code number or
ID) [0267] Polarization direction (e.g., horizontal, vertical, circular,
etc.)

[0268] Any event mentioned previously or hereafter that may cause the
transmitter to decide to change one or more channel quality information
parameters (e.g., number of partitions, number of values/coefficients per
partition, transformation parameters, number of transmitted
values/coefficients per partition, number of available/required bits for
channel quality information, etc.) may as well or instead cause the
management entity to decide a change of parameter(s) mutatis mutandis. In
case there is a change to the parameters, same may be conveyed to the
channel quality information transmitter using e.g., a control signal, as
outlined in the previous paragraph.

[0269] Generally, it may be also assumed that the scheduling and link
adaptation are performed on resource unit basis. For example, the
smallest unit of (radio) resources (also referred to as a resource block
or resource unit) that can be allocated in an OFDMA system is typically
defined by one subframe in time domain and by one subcarrier/subband in
the frequency domain. Similarly, in a CDMA system this smallest unit of
radio resources is defined by a subframe in the time domain and a code in
the code domain. Generally, a resource unit (for scheduling may) be
defined as a unit formed by a combination of at least two out of a
subframe in the time domain, a subcarrier/subband in the frequency
domain, a code in the code domain and antenna in MIMO.

[0270] It should be noted that the channel state/quality is reported for a
set of resource units into which the channel may be divided. These
resource units may or may not be similar to the resource units based on
which the mobile stations are scheduled and/or based on which link
adaptation may be performed. For example, assuming an OFDM shared
channel, the resource units for which the channel state is reported may
either correspond to the resource blocks based on which scheduling and/or
link adaptation is performed. Alternatively, the transmitting entity
(mobile stations) providing the channel state information may also report
the channel state on a resource unit-basis where the resource unit is
equivalent to one or more subframes in the time domain and one or more
subcarrier/subband in the frequency domain. This principle may also be
extended to the code domain. In other words, it is not prerequisite that
the granularity of the channel state report is identical to the
granularity in which resource may be scheduled in the system and/or link
adaptation is performed.

[0271] For communication in the mobile communication system e.g., an OFDM
scheme, a MC-CDMA scheme or an OFDM scheme with pulse shaping (OFDM/OQAM)
may be used. In some embodiments the scheduler may schedule the resources
on a per-resource block basis (i.e., per subframe basis in the time
domain) or on a transmission time interval (TTI) basis, wherein in the
latter case it may be assumed that a TTI comprises one or more subframes
in the time domain.

[0272] In one embodiment of the invention, channel quality information is
reported for a channel having 10 MHz bandwidth and consisting out of 600
subcarriers with a subcarrier spacing of 15 kHz. The 600 subcarriers may
then be grouped into 24 subbands (each containing 25 subcarriers), each
subband occupying a bandwidth of 375 kHz. Assuming that a subframe has a
duration of 0.5 ms, a resource block (RB) spans over 375 kHz and 0.5 ms.

[0273] Alternatively, a subband may consist of 12 subcarriers, 50 of those
subbands constituting the available 600 subcarriers. With a transmission
time interval (TTI) of 1.0 ms, equivalent to 2 subframes, a resource
block (RB) spans over 300 kHz and 1.0 ms in this example.

[0274] Another embodiment of the invention relates to the implementation
of the above described various embodiments using hardware and software.
It is recognized that the various embodiments of the invention may be
implemented or performed using computing devices (processors). A
computing device or processor may, for example, be general purpose
processors, digital signal processors (DSP), application specific
integrated circuits (ASIC), field programmable gate arrays (FPGA) or
other programmable logic devices, etc. The various embodiments of the
invention may also be performed or embodied by a combination of these
devices.

[0275] Further, the various embodiments of the invention may also be
implemented by means of software modules, which are executed by a
processor or directly in hardware. Also a combination of software modules
and a hardware implementation may be possible. The software modules may
be stored on any kind of computer readable storage media, for example,
RAM, EPROM, EEPROM, flash memory, registers, hard disks, CD-ROM, DVD,
etc.

[0276] In the previous paragraphs various embodiments of the invention and
variations thereof have been described. It would be appreciated by a
person skilled in the art that numerous variations and/or modifications
may be made to the present invention as shown in the specific embodiments
without departing from the spirit or scope of the invention as broadly
described.

[0277] It should be further noted that most of the embodiments have been
outlined in relation to a 3GPP-based communication system and the
terminology used in the previous sections mainly relates to the 3GPP
terminology. However, the terminology and the description of the various
embodiments with respect to 3GPP-based architectures is not intended to
limit the principles and ideas of the inventions to such systems.

[0278] Also the detailed explanations given in the Technical Background
section above are intended to better understand the mostly 3GPP specific
exemplary embodiments described herein and should not be understood as
limiting the invention to the described specific implementations of
processes and functions in the mobile communication network.
Nevertheless, the improvements proposed herein may be readily applied in
the architectures described in the Technical Background section.
Furthermore the concept of the invention may be also readily used in the
LTE RAN currently discussed by the 3GPP.